planetarium

American  

[plan-i-tair-ee-uhm] / ˌplæn ɪˈtɛər i əm /

noun

plural

planetariums, planetaria

1. an apparatus or model representing the planetary system.

2. a device that produces a representation of the heavens by the use of a number of moving projectors.

3. the building or room in which such a device is housed.

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planetarium British  

/ ˌplænɪˈtɛərɪəm /

noun

1. an instrument for simulating the apparent motions of the sun, moon, and planets against a background of stars by projecting images of these bodies onto the inside of a domed ceiling

2. a building in which such an instrument is housed

3. a model of the solar system, sometimes mechanized to show the relative motions of the planets

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Etymology

Origin of planetarium

1765–75; < New Latin, noun use of neuter of Latin planētārius planetary; cf. -arium

Explanation

A planetarium is a theater where you can look at images of planets, stars, and other celestial bodies on the dome-shaped ceiling. Planetariums host school field trips by day, and can even host Pink Floyd laser light rock shows by night. Use the noun planetarium for the projector that shines light onto the surface of the building's dome, recreating solar systems and constellations — and also for the building itself, where such a show is put on. Because planetarium is a Modern Latin word (from the roots planeta, or "planet," and -arium, "a place for,"), its plural can be either planetariums or planetaria.

Example Sentences

The material, alongside Russian-language sources and collaboration with other academics, including the University of Tartu and former astronomer Dr John Butler, formed the basis of the exhibition at the planetarium.

From BBC • Apr. 20, 2026

The launch comes as the planetarium unveiled plans for the UK and Ireland's first wraparound and completely immersive LED dome theatre.

From BBC • Apr. 1, 2026

Michelle Lopez’s video “Pandemonium” began life as a live performance inside a planetarium, and the film is a meditative look at man-made disasters.

From The Wall Street Journal • Mar. 6, 2026

A 37-year-old convict, who had more than a year still to serve for theft, fled on November 14 during an outing with fellow prisoners to the city's planetarium.

From Barron's • Nov. 28, 2025

I know from years of planetarium visits that craters on the moon were caused by asteroids and meteoroids crashing into the lunar surface, especially when the moon was very, very young.

From "Shine!" by J.J. and Chris Grabenstein